It’s been a while since a TV drama had me flinching at the screen from behind my fingers but the ripping finale of Ripper Street (BBC1) was like a prequel to Rocky set in Victorian times. If I’d been watching in 3D I’d have been out for the count, reeling from one of Det Sergeant Drake’s deadly uppercuts.

All other legal and legitimate efforts to nail the monstrous Det Insp Jedediah Shine having failed, it came down to a blood-spattered scrap, slow-motion firework sprays of blood striping the screen in a manner that would have made Dexter green with envy.

Full respect here to actors Jerome Flynn and Joseph Mawle and the visceral direction: if there’s been a more convincing boxing scene on British TV, I don’t recall it. This was a boxing bout with sledging that would put an Ashes encounter to shame, taunts about Drake’s dead wife stirring the passions of a man who had been striving to put his violent past behind him. The message was driven home with force: when pushed to extremes, the human condition will revert to its most craven instincts.

By the end Det Insp Reid, the erstwhile beacon of decency in the human cesspit Ripper Street takes perverse delight in sloshing about in, had been reduced to a savage, entreating his henchman Drake to ‘Kill him! Kill him! Kill him!’ as Shine staggered punchdrunk on the ropes. All Reid’s cultivated calm and suppressed rage at the iniquities of his daily toil blew like a volcano in a waistcoat.

Richard Warlow’s luxuriant dialogue is one of the joys of Ripper Street, multi-syllables scattering like marbles on the Victorian cobbles, but here he went for the gut. His guard was down and Reid, deftly played by Matthew Macfadyen, was revealed to be as morally compromised as those he’d been spending his life attempting to bring to heel.

It wasn’t the most upbeat way to end a fine show but it packed an emotional punch. If there was a message it belonged to Sergeant Artherton, a man with his own philosophy for getting through life: ‘All we may do is put one foot in front of the other, may we not?’